Remove unneeded import

Fixes clippy::legacy_numeric_constants.

src/sys/unix/selector/epoll.rs

@@ -5,7 +5,7 @@ use std::os::unix::io::{AsRawFd, RawFd};
 #[cfg(debug_assertions)]
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::Duration;
-use std::{cmp, i32, io, ptr};
+use std::{cmp, io, ptr};
 
 /// Unique id for use as `SelectorId`.
 #[cfg(debug_assertions)]